1. Field of the Invention
The present invention relates to a headrest-attached vehicle seat which is mounted in an automobile or the like. More specifically, it relates to a headrest-attached vehicle seat which is capable of restraining the head of an occupant, and if necessary, supporting the neck of the occupant suitably.
2. Description of the Related Art
Various structures have been proposed for a vehicle headrest or a headrest-attached vehicle seat. They are designed to protect an occupant, make the occupant feel comfortable, or for another such purpose.
For example, Japanese Utility Model Laid-Open No. 7-39606 specification has presented the following structure. To the top part of a seat back, a main portion is attached via a pole, and then, a side portion is attached to each of both sides of the main portion. These side portions can be turned in the seat's front-and-rear directions. The side portions are usually turned upward, so that it and the main portion can keep the head of an occupant in position. However, for example, when the vehicle corners, the occupant may receive great lateral G (i.e., inertia force in the right-and-left directions). Or, when the vehicle is running, the occupant in the passenger seat, the second-row seat or the like may be taking a nap so as not to keep the posture of the head. In such a case, the above described side portions are turned downward ahead of the seat, so that the occupant's head can be kept from swaying sideways.
According to Japanese Utility Model Laid-Open No. 7-39606 specification, as described above, if the side portions are turned downward ahead of the seat, the headrest can keep the head from swaying sideways beyond a predetermined range. But, it cannot support the occupant's neck. If the neck of the occupant (except the driver who is at the wheel) is supported when the occupant relaxes and takes the seat, that will lighten the occupant's supporting load on the head. Thus, the occupant can feel more comfortable. However, according to Japanese Utility Model Laid-Open No. 7-39606 specification, the headrest is not designed to support the occupant's neck. Thus, such an improvement in comfort as described above cannot be expected.
Taking this disadvantage into account, another headrest has been proposed, for example, in Japanese Patent Laid-Open No. 9-75167 specification. FIG. 9 is a perspective view of a headrest 190 which corresponds to the headrest according to Japanese Patent Laid-Open No. 9-75167 specification. The headrest 190 includes a headrest body 194 which is attached, via a pole, to the upper part of a seat back. Below the headrest body 194, an auxiliary portion 195 is provided which has a substantially concave shape so as to cover the headrest body 194 from both right-and-left sides and from below. In addition, the auxiliary portion 195 can be turned on a pivot 191 below the headrest body 194. At the time of regular use, the auxiliary portion 195 is turned upward, so that it is located on both right-and-left sides and below the headrest body 194 (see a chain double-dashed line in the figure). Thereby, it can restrain, together with the headrest body 194, the head of an occupant. On the other hand, for example, in the case where great lateral G is applied to the occupant, the auxiliary portion 195 is turned downward ahead of the seat, so that it extends ahead of the seat from below the headrest body 194. Thereby, both end portions 193 on both right-and-left sides of the auxiliary portion 195 prevents the occupant's head from swaying laterally. At the same time, a middle portion 192 in the middle of the auxiliary portion 195 restrains the occupant's neck.
Herein, the auxiliary portion 195 can be switched from an unused posture (see the chain double-dashed line) in which it stands above the pivot 191 to an in-use posture (see a solid line) in which it is turned forward by substantially 90 degrees from the unused posture, and vice versa. Besides, it is supposed to turn and stop midway, so that it can also be used in such a posture.
According to Japanese Patent Laid-Open No. 9-75167 specification which is described above, the auxiliary portion 195 is switched to the in-use posture. Thereby, the occupant's neck, head, body and the like can be fixed, thus helping the occupant get some sleep. But, such a headrest 190 needs to have a mechanism for constantly adjusting the position of the auxiliary portion 195 suitably for the occupant's body shape or sitting posture.
However, there is a disadvantage in that the headrest 190 does not have an enough function to adjust that position. For example, let's consider a case in which an adjustment in the up-and-down directions is made when the occupant's neck is supported on a front-end portion 192a of the middle portion 192. That adjustment can be easily made by moving the headrest 190 itself up and down with respect to the seat back. In contrast, an adjustment in the front-and-rear directions is difficult to make. If the in-use posture of the auxiliary portion 195 is standardized as the state in which it is turned forward by 90 degrees from the unused posture, then in the in-use posture, the front-end portion 192a will not have any front-and-rear positioning function. Besides, even if it is turned back and forth slightly from the in-use posture, then the front-end portion 192a moves simply in the up-and-down directions. In other words, it makes only a few moves in the front-and-rear directions. This is because the posture in which the auxiliary portion 195 is substantially horizontal is defined as the in-use posture. In that case, the tangential line of the turning circle of the front-end portion 192a extends substantially in the vertical directions.
Herein, it can be considered that the in-use posture of the auxiliary portion 195 is widened up to an almost vertical upright state. Thereby, the auxiliary portion 195 is largely turned within the range of the wider in-use posture. In that case, it appears as if the positional-adjustment width of the front-end portion 192a has become greater in the front-and-rear directions. However, such an increase in the positional-adjustment width in the front-and-rear directions as described below, can make the whole headrest 190 larger. This may cause a harmful effect, such as narrowing the driver's rear-view field. Hence, the above described disadvantage cannot be resolved.
As shown in FIG. 9, when the auxiliary portion 195 stays upright, the middle portion 192 is located at about half the height of the headrest 190. This structure is necessary for securing a certain distance (or turning radius) between the pivot 191 and the front-end portion 192a (i.e., if this turning radius is short, the positional-adjustment width in the front-and-rear directions is not expected to become greater, even though the range of the in-use posture is widened close to the upright state. In short, it is impossible to support the neck adequately, which is located ahead of the back of the head). If the neck is supported when the auxiliary portion 195 stays nearly upright, the back of the head lies apart above the front-end portion 192a. In order to restrain the back of the head in such a high position, the headrest body 194 has to be placed in a higher position. In that higher position, the occupant's head which tends to sway up and down or from side to side when the vehicle is running, needs to be kept in position. To do that effectively in such a higher position, the headrest body 194 must be longer in the right-and-left directions. In other words, the headrest body 194 becomes larger, thus resulting in the headrest 190 being large-sized.
If the headrest 190 becomes larger, that will narrow the rear or front view-field of the driver or the occupant. For example, let's assume that a large-sized headrest 190 is used for the second-row seat or a rear seat behind it. In that case, when the driver confirms the rear view by looking back or using a rearview mirror provided in a front header, a larger part of the viewing field is obstructed by the headrest 190. In short, the rear-view field becomes narrower. Besides, for example, let's assume that a large-sized headrest 190 is used for a seat (including the passenger seat) ahead of the rearmost seat. In that case, the front-view field of an occupant who sits behind the front seat becomes narrower, thereby making the occupant feel oppressed.
As described above, in the structure according to Japanese Patent Laid-Open No. 9-75167 specification, unless a head rest is made larger, it cannot have an adequate adjustment width. Hence, an occupant's neck is difficult to properly support.